Phenolic and Urea compounds are included in thermosetting plastic closures.These plastics have proven themselves to have the following characteristics:

  • Widest range of chemical compatibility.
  • Widest range of temperature tolerance of the plastic closures.
  • Will withstand sub-zero temperatures without embrittlement.
  • Will withstand temperatures to 300¡ with proper liner selection.
  • Provide the most consistent adherence to close tolerance specifications.
  • The rigidity of thermosetting plastics helps guard against slipping over threads, which can be a problem with thermoplastic closures, particularly polyethylene. This problem is aggravated with polyethylene bottles when thread depth, or neck diameters are not accurate.

Phenolic closures are available in black and brown. Urea closures are available in white and other light colors. When closures are to be metallized, phenolics seem to give better results. The "heft" of the thermoset closure also adds to the feel of quality and superiority.


Among the major resins considered for the caps and closures are the following:


Accounting for the largest share of plastic used (over 60 percent), the resin is best characterized by good clarity, excellent moisture and chemical resistance, high softening point and outstanding dimensional stability. It has been adapted to a broad assortment of food, pharmaceutical and beverage applications, and dominates the child-resistant and tamper-evident fields with sealing characteristics comparable to metal.

Though most polypropylene closures are lined, in controlled circumstances linerless closures eliminate the cost of material and inserting of liners. The economies can be worthwhile. It is important that the neck finish of the container mate properly and consistently with the closure. Pre-testing and "on-going" quality control checks of both the container and closure are important when choosing
this option.


The second most widely used resin within the industry, polystyrene exhibits good clarity, low moisture absorption, smooth surface qualities and ease of processing. Principal applications include overcaps, lid and screw caps for non-oxygen sensitive materials. Demand for polystyrene is expected to slowly decline through the decade as packagers continue to upgrade for improvements in impact and heat properties.


High density (HDPE) brings strong impact, rigidity, good chemical resistance and excellent drug compatibility to the field and is frequently utilized for threaded screw caps, shrink bands and laminated liners. Meanwhile, low density (LDPE/LLDPE) is known for its impact resistance and flexibility. It is especially useful for closures requiring storage at low temperatures. The increasing penetration of polypropylene is expected to continue to depress future growth in caps and closures for the polyethylenes.

Polyvinyl Chloride (PVC)

Providing good barrier strength and colorability, PVC has gained position in several high-quality applications and is expected to show continued growth from a relatively small position (less than 5 percent) within the industry.

Regulatory Specifications

Many end-use applications for polypropylene closures require food contact. Regulation 177.1520 of the Food and Drug Administration (FDA) covers the use of certain resin grades and additives for this use. The Drug Master File also lists certain resins which have approval for packaging of this type. These regulations may well narrow the list of suitable materials for a specific application and should be considered early in the search process.

The many variations within the four major headings above can make the material selection process for a specific closure application seem overly complex, when in fact the closure supplier has an abundance of assistance to call on beyond just the experience factor.

Metal Closures

Metal closures are available in Tinplate.


  • Offers outstanding opportunities for decorating, or as label substitute.
  • Has the widest range of temperature tolerance.
  • The most resistant to fracture from impact.
  • The most economic lined closure.
  • Widespread use over a long term implies: utility, acceptance, and reliability.


  • Tinplate closures are subject to attack by acids, caustics, and moisture if coating is ruptured.
  • On Polyethylene bottles, particularly with 38mm openings and larger, close tolerances need to be maintained.


Many products such as fragrances, personal care products, window cleaners, waxes, insecticides, herbicides, etc. are designed for use as sprays. The finger tip sprayer very often is ideal for this purpose. Some models are designed as "shipper units," and need no special packaging. Others that are auxiliary components are sold separately, or included with an economy size pack or concentrate, do not include the sealing feature of the shipper, but are more economical.

Fine Mist Sprayers provide an excellent alternative to aerosol packaging, and have met great acceptance in
the market.

Trigger Sprayers fill the need where a large spray pattern is required, or where the spraying is on-going over a period which would cause fatigue if a finger tip sprayer were used.


The diversified selection of dispensing closures offer great opportunities for convenience and function. They range from dispensers which provide for a stream, ribbon, drop or spray application of a product to shaker fitments for sprinkling dry products.

Besides covering a broad range of products from glue to spices, there are many specialized situations which can be met by the use of a dispensing closure such as in one handed applications or in dispensing controlled amounts of a product.

The convenient use of a product in its most effective form of application can be the key to market acceptance. For this reason, functional closures should be given careful consideration for inclusion as part of any package. Since many variables affect the compatibility and success of any given combination of product and closure, testing is a crucial step. Many dispensers involve moving, or mating parts as well as critical orifices so one consideration should be simulating conditions in which the product will be used and also accelerated testing for estimated shelf life.

This information can narrow the selection process.